How to Add, Subtract, Multiply and Divide Fractions (With Mixed Numbers)
A clear method for fraction arithmetic and a calculator that shows the simplified fraction, mixed number and decimal.
Fractions are easy once you learn four rules. The calculator below gives you the answer and the steps you can check against your homework.
Quick answer
Add or subtract after making the denominators equal. Multiply tops and bottoms. Divide by multiplying by the reciprocal. Then simplify.
The rules
Add and subtract. Use a common denominator. 1/3 + 1/4 = 4/12 + 3/12 = 7/12.
Multiply. Multiply numerators and denominators. 2/3 × 3/5 = 6/15 = 2/5.
Divide. Flip the second fraction and multiply. 3/4 ÷ 2/5 = 3/4 × 5/2 = 15/8 = 1 7/8.
Mixed numbers. Convert to an improper fraction first: 2 1/3 = 7/3.
Using the calculator
- Enter the first fraction or mixed number.
- Choose +, −, × or ÷.
- Enter the second fraction.
- Read the answer as a simplified fraction, a mixed number and a decimal.
Simplifying
Divide the top and bottom by their greatest common factor. 12/18 has a GCF of 6, so it becomes 2/3.
Common mistakes
- Adding denominators (1/2 + 1/3 is not 2/5).
- Forgetting to flip the second fraction when dividing.
- Leaving an answer unsimplified in exams.
- Forgetting the whole number in a mixed number.
Everyday uses
Recipes (1/2 cup + 3/4 cup), carpentry (3/8 inch cuts) and sharing (2/5 of a bill).
